The invention relates to an electric contactor device including fixed electric contacts and a movable electric contact which is disposed for abutment against the fixed contacts. In particular, while not limited thereto, the invention relates to an electric signal generator including fixed electric contacts formed on a printed circuit board and an electric slider contact carried by a rotor and disposed for abutment against the fixed electric contacts.
Such an electric signal generator may be utilized as a throttle opening sensor which is connected to a throttle valve of an engine, one example of which is disclosed in U.S. Pat. No. 4,345,240 issued to Hiroyuki Amano et al. The throttle opening sensor includes a plurality of split electrodes formed on a printed electrical circuit board and an electrically conductive slider having a plurality of radially extending legs which fixedly carry contact members disposed for contact with the plurality of split electrodes. The electrically conductive slider is secured to a shaft which is in turn fixedly mounted on the rotatable shaft of a throttle valve. The potential of the slider is maintained at a ground potential while the split electrodes assume the ground potential only when they are engaged by contact members on the slider. In this manner, the output is in the form of a bi-level signal, and the combination of outputs from the split electrodes constitute together a code corresponding to the opening of the throttle valve.
Generally, the throttle opening sensor is mounted on an engine or is disposed very close to the engine, and thus is subject to heat radiation therefrom to raise its temperature. The plurality of split electrodes formed on a printed electrical circuit board comprises a conductor on the circuit board formed by a copper foil, which is then plated with nickel, and the nickel plating is in turn plated with gold or palladium. The nickel plating has a relatively high level of abrasion resistance but exhibits a relatively low level of corrosion resistance and a relatively high contact resistance, which is the reason to provide the gold or palladium plating or coating thereon. As is well recognized, a gold plating exhibits an increased corrosion resistance and a reduced contact resistance, but since it has a low level of abration resistance, it is applied as a relatively thick coating. Because both gold and palladium are relatively expensive, the described throttle opening sensor requires an increased cost for the materials.